1. Field of the Invention
The invention relates to a process for the preparation of organylhydrogensilanes via a comproportionation reaction.
2. Background Art
The demand for organylhydrogensilanes, in particular for methyldichlorosilane and dimethylchlorosilane, is substantially higher than the amount obtained as byproducts in the direct synthesis by the Müller-Rochow process.
Comproportionation reactions of organylchlorosilanes with hydrogenchlorosilanes to give organylhydrogenchlorosilanes using Lewis acids as catalysts are described in WO 99/31111. The process is not very selective, and many byproducts are formed. The preferred AlCl3 catalyst is volatile and sublimes. Since inhibitors are necessary as additives, these are added during distillation.
In DE 19520737 A, the comproportionation reaction to give organylhydrogenchlorosilanes is carried out using HCl-saturated catalysts based on Zr/Al oxide. High reaction temperatures are used. This leads to the use of a large amount of energy and, owing to the lower selectivity, to more waste products.
DE 2132335 A describes the reaction of methyltrichlorosilane and dichlorosilane to give methyldichlorosilane in the presence of hydrochlorides of tertiary amines as catalysts. The catalytic activity is low and the secondary reaction of the methyldichlorosilane product with the HCl present in the catalyst to give methyltrichlorosilane and hydrogen leads to low yields.
DE 1264442 A describes comproportionation reactions of silanes with quaternary ammonium and phosphonium salts, but no specific process for the preparation of organylhydrogenchlorosilanes is disclosed.
U.S. Pat. No. 4,605,543 A describes comproportionation reactions starting from methyldichlorosilane with quaternary ammonium and phosphonium salts.
EP 776698 A describes a process in which, in a comproportionation reaction, the hydrogen is transferred to the compound whose silicon atom carries the larger number of organic substituents. The “hydrogenating agent” is methylsilane or methylchlorosilane, which is produced by disproportionation of methyldichlorosilane.